Pressure transmitting fluids



Powder Company, Wilmington, DeL, a corporation of Delaware ApplicationDecember 2, 1954 Serial No. 472,773

6 Claims. (Cl. 252-78) No Drawing.

This invention relates to pressure transmitting fluids and moreparticularly to pressure transmitting fluids of low flammability.

This application is a continuation-in-part of application Serial No.407,109, filed January 29, 1954, now U. S. Patent 2,767,145. 1 I

' It is the object of the invention to provide pressure transmittingfluids which are essentially non-flammable and which may be' utilizedover a wide range of tern-- peratures andlparticularly at'lowtemperatures.

' The pressure transmitting fluids of the invention may conveniently bethought of' as comprising a base liquid or solvent containing dissolvedadditives for specificpur: poses and they will be so described inthisspecification. The said base liquid is aternary composition of ethyleneglycol, water and formanride containing from 6% to 40% water, from 20%to .75% ethylene glycol and from 4% to 55% formamide, to a total of100%, all percentages being by weight. Preferred base liquids within thebroad range so defined are those containing from 20% to 35% water, atleast 10% formamide and at least 30% ethylene glycol.

To provide properties of fluidity desirable Where extremes oftemperature are encountered, the pressure transmitting fluids of theinvention contain viscosity index improvers. Suitable viscosity indeximprovers are high molecular Weight compounds of elongated molecularstructure which are soluble in the base liquid abovedefined. Among such.maybe named the higher polyethylene glycols, particularly those rangingupwards from 3,000 in molecular weight;1soluble gums such as gum arabicor gum. tragacanth; cellulose derivatives, particularly sodium 'carboxymethyl cellulose; linear polymeric acids, particularly polyacrylic acid;and polyglycol esters of high molecular weight carboxylic acids.Preferred viscosity index improvers in composition of the invention arepolyoxyethylene ether-esters of dimerizcd higher unsaturated fattyacids. Such ether-esters may be conveniently prepared by the directaddition, at elevated tempera'ture and'pressure, ofethylene oxide to thedimerized acids. Particularly preferred are the condensationprodnets offrom 20 to 35 mole of ethylene oxide with one mol of linoleic aciddimer. v

The contentof' viscosity index however in pressure transmitting fluidsin accordance Withthe invention may vary over a considerablerangedepending upon the choice of improver, the composition of the baseliquid, and? the use to whichthe fluidis" to be put. Thus, a fraction ofa. percent of medium viscosity carboxymethyl cellulose (sodium salt) isas eflectivewith respect. to increasing i i Which the fluid is employed.Suitable concentrations 2,841,560 ?ai:ented July 1, 1958 having anaverage molecular weight of 6,000. SEIilSfEC- tory fluids will beobtained, in general, it sufiicient vis cosity improver is added: to thebase liquid to adjust its viscosity to between about 2 and about 150centistokes at F.

In addition to the base liquid and viscosity index improver hereinbeforedescribed, the pressure transmitting fluids of the invention may containoptional ingredients added for specific purposes. Among such may benamed corrosion inhibitors, boundary lubricants and cloud pointinhibitors.

Among the known corrosion inhibitors are organic amines such asmorpholine or the ethyl ethanolatnines, inorganicnitrites, organicnitrites, sodium benzoate, ethyl benzoate or ethyl paramino benzoate.Particularly effective as an inhibitor against corrosion of copper andcopper containing alloys is sodium mercaptobenzothiazole. The above andother corrosion inhibitors may be em: ployed singly or in combination,and in the proportions necessary to protect the particular hydraulicsystemin range from 0.1% by weight up to 3%.

Boundary lubricant additives are particularly desirable to reducepump-wear in hydraulic systems where hydraulic fluids are circulated athigh velocities. Petroleum sulfonates are particularly suitable for thispurpose and may conveniently be employed in concentrations of from 1% to3%. r

The components of base liquids of the pressure trans mitting fluidsproduced in accordance with the invention are compatible over widetemperature ranges but frequently the compounded fluids show a tendencyto become cloudy and show phase separation at elevated ternperatureswhen the viscosity index improver coutaius polyoxylalkylene radicals. toinclude in fluids containing such improvers, especially if they are tobe employed at elevated temperatures, up to 5% by weight of an additiveto prevent clouding and phase separation. Salts of alkyl aryl sulfonicacids and particularly amine salts of such acids have been found veryefiective as retarders and inhibitors of cloud formation at elevatedtemperatures. Also effective are the amine salts of acid sulfates oflower polyglycol ethers of highly branched aliphatic alcohols.Particularly to be named in this connection are the sodium and isopropylamine salts of dodecyl benzene sulfonic acid, and the isopropyl aminesalt of sulfated triethylene glycol monoether of a highly branchedtridecyl alcohol.

Specific examples of pressure transmitting fluids for use underconditions of sub-zero temperatures and prepared in accordance with theinvention are presented in Table I. The superiority of the preferredpolyoxyethylene ether-esters of linoleic acid dimers as viscosity indeximprovers is evident from inspection of the tabulated data. Employingcompound B at the 15% level, fluids with viscosities as high as 36centistokes at 130 F. can be obtained which are satisfactorily fluid atf65 F. '(visc'osity=1,000 to 1,500 centistokes). lily-employing less ofthe same or: related compounds (atlevels of 7.5 to 10%) viscosities of400 to 1,000 centistokes at the very low temperature of .65 F. can beobtained in com.- positions exhibiting viscosities of 4 to 10centistokes at 130 F.

Accordingly, it is expedient Table 1 Composition of Base LiquidComposition of Fluid Viscosities (Centistokes) Ex mple ViscosityImprover Freezing No. Ethylene Forma- Water, Base Point, F.

Glycol, mide, Percent Liquid, Percent Percent Percent Oom- Percent at atpound 130 F. 65 F 48 32 20 90 A 10 83 3. 9 663 42 24 34 90 B 10 83 6. 9529 57. 12. 5 3O 92. 5 B 7. 5 below 100- 9.0 1, 036 56 36 8 90 B -82 6.9 1, 817 30 40 30 90 C 10 2. 8 408 30 40 30 90 D 10 2. 8 912 30 40 30 90E 10 1. 8 388 30 40 3D 90 B 10 7. 3 453 40 40 90 B 10 6. 4 946 50 20 99.5 F 0. 5 4. 2 1, 665 60 30 20 90 G 10 5. 4 2, 040 60 30 20 99 H l. 0 10.1 l, 809 48 20 32 85 B 15 35. 8 1, 355 42 23 85 B 15 36. 0 1, 034

The viscosity improving compounds are coded as follows:

A=Polyoxyethylene ether-ester of linoleic acid dimer (Emery 955 DimerAcids) containing 28 oxyethylene groups B=Polyoxyethylene ether-ester oflinoleic acid dimer (Emery 955 Dimer Acids) containing 24 oxyethylenegroups.

C =Polyoxyethylene ether-ester of tall oil acids containing 16oxyethylene groups.

For the operation of hydraulic machinery indoors where the extremely lowtemperatures mentioned in the foregoing paragraphs and in Table I arenot encountered fluids of higher viscosity at elevated temperature maybe Sod. dodecyl benzene sulfonate (33 /a% aq. solution) 6.0 Sod.mercaptobenzothiazole 0.2

This solution after equilibriation for 5 days had a cloud point of morethan 210 F. and a viscosity at 130 F. of centistokes. 7

EXAMPLE 16 Substitution of viscosity improver B (see Table I) forviscosity improver A in the formula of Example 15 produced a fluid Witha cloud point of 195 F. and a vis cosity at 130 F. of 109 centistokes.

When employing the preferred polyoxyethylene etheresters of linoleicacid dimer as viscosity-index improver, it is found that viscositiesincrease as the ratio of glycol to formarnide in the base liquidincreases. In Table II there are presented the viscosities at threetemperatures of a series of compositions of constant water content andconstant viscosity improver content wherein the proportions of glycoland formamide vary over a considerable range. The viscosity improver isthe polyoxyethylene ether-ester containing 24 oxyethylene groups per molof a dimerized unsaturated acid available from Emery Industries underthe designation Empol 1022.

Mixed polyoxyethylene-polyoxypropylene ether-ester of tall oil acids.

Further, to illustrate the effect of salts of dodecyl benzene sulfonicacid on the high temperature stabilization of fluids in accordance withthe invention, the following examples are presented. A hydraulic fluidwithout cloud point inhibitor consisting of 9% of the polyoxyethyleneether-ester (containing 24 oxyethylene groups per mol) of linoleic aciddimer in 91% of a base liquid comprising 41% ethylene glycol, 27.5%formamide and 31.5% water was found to become cloudy and separate intophases at temperatures above F. The several inhibitors in theproportions, indicated in Table HI, were added and the cloud pointsdetermined.

Table III INHIBITION OF HIGH-TEMPERATURE CLOUDIN G Example Cloud N o.Inhibitor Point,

21 2% isopropyl amine dodecyl benzene su1ionate 200 2% hexylaminedodecyl benzene sulfonate 180 4% hexylarnine dodecyl benzene sulfonate210 2% methyl glucamine dodecyl benzene sulfonate.

The foregoing examples are illustrative only and are not presented byway of limting the scope of the invention. Those skilled in the art willrecognize that many variations on the specific formulas recited can beprepared to produce hydraulic fluids adapted to a wide range ofparticular uses.

What is claimed is:

l. A pressure transmitting fluid comprising a base liquid consisting ofat least 25% ethylene glycol, at least 10% formamide and from 20 to 35%Water, all percentages being by weight, and a polyoxyethylene etheresterof a dimerized higher unsaturated fatty acid, said ether-ester beingsoluble in said base liquid and present in suflicient quantity to adjustthe viscosity of the fluid at 130 F. to between about 2 and aboutcentistokes.

2. A pressure transmitting fluid as in claim 1 wherein I there ispresent up to 5% by weight of a cloud point inhibitor selected from thegroup consisting of salts of alkyl aryl sulfonic acids and amine saltsof acid sulfates of lower polyglycol ether of highly branched aliphaticalcohols.

3. A pressure transmitting fluid as in claim 2, wherein the cloud pointinhibitor is an alkyl aryl sulfonate.

4. A pressure transmitting fluid as in claim 2 wherein the cloud pointinhibitor is sodium dodecyl benzene sulfonate.

5. A pressure transmitting fluid comprising a base liquid consisting ofat least 20% ethylene glycol, at least formamide and from to water, allpercentages being by weight, and sufficient of a polyoxyethyleneether-ester of dimerized linoleic. acid containing from 20 to -35oxyethylene groups per mol to adjust the viscosity of the fluid at F. tobetween about 2 and about centistokes.

6. A pressure transmitting fluid comprising a base liquid consisting ofat least 30% ethylene glycol, at least 10% formamide and from 20 to 35%water, all percentages being by weight, and from 7.5 to 15% by weightbased 6 on the total fluid of a polyoxyethylene ether-ester of dimerizedlinoleic acid.

References Cited in the file of this patent UNITED STATES PATENTS1,687,094 Isermann Oct. 9, 1928 2,205,183 Woodhouse June 18, 19402,308,246 Polin et a1. Jan. 12, 1943 2,588,970 Esposito Mar. 11, 19522,755,251 Barker July 17, 1956 FOREIGN PATENTS Great Britain Dec. 29,1930

1. A PRESSURE TRANSMITTING FLUID COMPRISING A BASE LIQUID CONSISTING OFAT LEAST 25% ETHYLENE GLYCOL, AT LEAST 10% FORMAMIDE AND FROM 20 TO 35%WATER, ALL PERCENTAGES BEING BY WEIGHT, AND A POLYOXYETHYLENE ETHERESTEROF A DIMERIZED HIGHER UNSATURATED FATTY ACID, SAID ETHER-ESTER BEINGSOLUBLE IN SAID BASE LIQUID AND PRESENT IN SUFFICIENT QUANTITY TO ADJUSTTHE VISCOSITY OF THE FLUID AT 130*F. TO BETWEEN ABOUT 2 AND ABOUT 150CENTISTOKES.